The operating efficiency of a turbocharged multi-cylinder internal combustion engine may be increased by dividing the engine cylinders into at least two groups and, at low loads, deactivating one group of cylinders. The exhaust lines of the two or more groups may be arranged to couple with a two-channel turbine such that the deactivable group of cylinders is attached to one channel and the active group is attached to the other channel.
One example approach to increase the operating efficiency of the engine is to deactivate a group of cylinders using variable valve drives, wherein the charge air mass which flows into the combustion chamber during the intake process is controlled by the inlet valve lift and the exhaust gas which flows into the exhaust system is controlled by the exhaust valve lift. The valves therefore remain in a closed position during deactivation of the cylinders and block exhaust flow from the deactivated cylinders to the turbine. Another example approach to increase the operating efficiency of the engine is to deactivate a group of cylinders by stopping the fuel supply and/or the applied ignition to the cylinders. Here, the deactivated cylinders continue to participate in the charge exchange if the associated valve drive of the cylinders is not deactivated or may not be deactivated. Therefore, charge air may be passed to the turbine of the turbocharger.
A potential issue noted by the inventors with the variable valve drive approach above is the cost associated with implementing them, thus variable valve drives may be unsuitable for series production. Further, variable valve drives reduce the overall mass flow to the turbocharger during a partial deactivation, reducing the turbine pressure ratio. Another potential issue noted by the inventors when the fuel supply and/or the applied ignition is stopped to deactivate the cylinders is that the cylinders still participate in the charge exchange, which has the effect of decreasing the benefits of the partial deactivation. Another potential issue noted by the inventors is that the pressure pulses may attenuate in the two-channel turbine when each group of cylinders (e.g. the deactivable and active cylinder groups) is coupled to a channel, during a partial deactivation of the engine.
A potential approach to at least partially address some of the above issues includes a supercharged internal combustion engine comprising at least two cylinders, in which each cylinder has at least one outlet opening adjoining an exhaust line for discharging exhaust gases via an exhaust-gas discharge system and at least one inlet opening adjoining an intake line for the supply of charge air via an intake system. The cylinders are configured in such a way that they form at least two groups with in each case at least one cylinder, wherein the at least one cylinder of the first group is a cylinder which is in operation even in the event of a partial deactivation of the internal combustion engine and the at least one cylinder of a second group is formed as a cylinder which can be switched in a load-dependent manner. An exhaust-gas turbocharger is provided which comprises a turbine arranged in the exhaust-gas discharge system and a compressor arranged in the intake system. The exhaust lines of the cylinders of each cylinder group merge in each case to from an overall exhaust line such that an exhaust manifold is formed and the two overall exhaust lines are connected to a two-channel turbine. The two-channel turbine comprises at least one rotor mounted on a rotatable shaft in a turbine housing, in such a way that in each case one overall exhaust line is connected to one of the two inlet openings of the turbine, wherein each inlet opening is adjoined by one channel of the turbine. A first shut-off element is provided, which in a first working position blocks the channel assigned to the second cylinder group and separates the channel from the at least one rotor and in a second working position, opens up the channel and connects the channel to the at least one rotor. Further, at least one exhaust-gas recirculation arrangement may be provided.
As an example, the fuel supply and applied ignition may be stopped to deactivate the switchable cylinders when the engine is operating below a threshold load for a time period to enact a partial deactivation. During the partial deactivation, the shut-off element may be adjusted to change a degree of fluid coupling between the channel and the exhaust line of the switchable cylinders. The control of the exhaust flow of the deactivable cylinders in response to engine load keeps pressure pulses from attenuating in the turbine of the turbocharger and removes the need for the cylinders to be mechanically closed, thereby improving the overall engine efficiency. Further, the exhaust emissions may be decreased during partial deactivation by blocking the channel.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.